Hemostatic bipolar electrosurgical techniques are known for reducing bleeding from incised tissue prior to, during, and subsequent to incision. Such techniques generally pass a high voltage-high frequency current through a patient's tissue between two electrodes for cutting and coagulating the tissue. This current causes joulean heating of the tissue as a function of the current density and the resistance of the tissue. Heat deposited in the tissue coagulates the blood in the vessels contained in the tissue, thus reducing the blood flow from severed vessels and capillaries.
In previously known electrosurgical systems, a generator typically supplies a high voltage, high frequency voltage waveform to an electrosurgical instrument to cause a current to pass through the patient's tissue in the form of a high voltage electric arc. A drawback of such systems, however, is the tendency of the current arc to promote charring of the tissue, thus inhibiting rapid regrowth of the tissue.
Another drawback of previously known electrosurgical systems is a tendency of the coagulated blood and severed tissue to adhere to the working surfaces of the instrument, due to wide variations in peak-to-peak voltage waveform supplied by the generators. This "coagulum" buildup increases the electrical resistance of the path along which current flowing between the electrodes of the electrosurgical instrument must travel, resulting in reduced hemostasis, ineffective cutting action, or both.
Yet another drawback of previously known electrosurgical systems is a tendency of tissue to adhere to the instrument as a result of initially high open-circuit voltages that occur when an electrosurgical instrument, powered by a conventional generator, is energized before the instrument electrodes are brought into contact with the patient's tissue. This "sticking" problem can limit maneuverability of the instrument and cause tearing of previously congealed tissue, thereby reactivating blood flow from that tissue.
Previously known electrosurgical generators typically provide monopolar and bipolar modes of operation in which they supply high frequency (above 100 kHz) alternating-current (AC) voltages in the range of 150 to 5000 volts peak-to-peak (or higher) at power ratings of less than 400 watts. The highest levels of peak-to-peak voltages typically result from energizing the electrosurgical generator before the electrodes are brought into contact with tissue. Examples of such generators are provided in Malis et al. U.S. Pat. No. 4,590,934, Schneiderman U.S. Pat. No. 4,092,986, Farin U.S. Pat. No. 4,969,885. See also, for example, the Operator's Manual for the Valleylab Force 2.RTM. and Force 4.RTM. generators.
There are in addition some previously known special purpose electrosurgical generators for reducing coagulum buildup and sticking when used with particular instruments. For example, Herczog U.S. Pat. No. 4,232,676 describes an electrosurgical scalpel and a special purpose low voltage generator in which power supplied to the scalpel is regulated by varying the frequency of the output voltage waveform. Similarly, Auth U.S. Pat. No. 4,492,231 describes a bipolar coagulator and special purpose low impedance generator that provides a low crest factor, low output voltage waveform to the coagulator to reduce coagulum buildup and sticking.
A drawback inherent in the electrosurgical systems described in the aforementioned Herczog and Auth patents is that each requires a special purpose electrosurgical generator which is developed for the particular electrosurgical instruments described in those patents. Likewise, any advantages provided by the generators described in the above-mentioned patents are offset by the practical consideration of having to purchase such generators, rather than being able to modify a large installed base of more conventional generators.
It would therefore be desirable to provide simple to use, low-cost adaptors for use with standard commercially available electrosurgical generators that would reduce problems with coagulum buildup and sticking encountered when using most electrosurgical instruments.
It further would be desirable to provide adaptors that could be connected between the monopolar or bipolar output jacks of standard commercially available electrosurgical generators and most electrosurgical instruments to modify the voltage waveforms supplied to the instruments to reduce coagulum buildup and sticking problems.